Abstract
To study the relationship between the onset of an increase in dyspnea and ventilatory threshold (VT) in children with congenital heart impairment, sixteen young subjects underwent a cardiopulmonary exercise test with dyspnea perception and ventilatory gas exchange assessments. Dyspnea score was measured from a visual analogical scale at rest and during each step of an incremental exercise test. Dyspnea score was plotted against oxygen uptake and the onset of an increase in dyspnea (DT) was determined when a brutal disruption occurs on the dyspnea score-oxygen uptake curve. VT was defined from gas exchange according to Beaver's method [[7 2 ), pulmonary ventilation (V·E), heart rate (HR), oxygen pulse (O2 pulse = V·O2 /HR), carbon dioxide production (V·CO2 ) and power output (P) were measured both at VT and DT effort level. Results pointed out that there was no significant difference between the cardiorespiratory variables measured respectively at VT and DT: V·O2 (VTV·O2 = 16.71 ± 2.65 vs. DTV·O2 = 18.34 ± 5.74 ml · kg-1 · min-1 ), V·E (VTV·E = 24.33 ± 6.86 vs. DTV·E = 26.82 ± 9.59 l · min-1 ), (VTV·CO2 = 789.31 ± 165.17 vs. DTV·CO2 = 924.02 ± 342.28 ml · min-1 ), HR (VTHR = 116 ± 10 vs. DTHR = 123 ± 20 beat · min-1 ), O2 pulse (VT O2 pulse = 7.83 ± 2.00 vs. DT O2 pulse = 8.01 ± 2.13 ml · kg-1 · beat-1 ), and P (VTP = 43 ± 16 vs. DTP = 52 ± 27 W). Moreover, the cardiorespiratory variables measured at DT and VT were closely related: V·O2 (r = 0.64, p < 0.01), V·E (r = 0.51, p < 0.01), HR (r = 0.75, p < 0.02), O2 pulse (r = 0.90, p < 0.001), and P (r = 0.80, p < 0.01). In addition, according to Bland and Altman's procedure [[8
Key words
Congenital heart disease - ventilatory threshold - dyspnea threshold - dyspnea rating
References
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